The present invention relates to platinum group metal catalyzed room temperature addition-curable silicone adhesive compositions employing an N-heterocyclic silane, such as 2,6 bis(trimethoxysilyltrimethyleneoxy) pyridine, as an adhesion promoter, and to such bis silyl pyridine adhesion promoter compositions.
As shown by Kasuya, U.S. Pat. No. 3,284,406, the adhesion of a cured platinum catalyzed addition-curable silicone composition onto a substrate is achieved by effecting the cure of the silicone composition at a temperature in the range of at least 70.degree. C. and preferably at least 100.degree. C.
Mitchell et al, U.S. Pat. No. 5,164,461, which is incorporated herein by reference, is directed to the use of certain silylmaleates, silylmaleimides or silylfumarates, such as bis[3-(trimethoxysilyl)alkyl] fumarates as adhesion promoters in addition-curable silicone adhesive compositions. Although the addition-curable silicone compositions of Mitchell et al have been found to be self-bonding to various substrates, such as plastics, metals or glass, these silicone adhesive compositions also require a temperature of about 100.degree. C. to about 150.degree. C. to effect a satisfactory cure.
It would be desirable therefore to provide platinum group metal catalyzed addition-curable silicone adhesive compositions which would bond satisfactorily onto an unprimed substrate, such as plastic or metal when applied thereto at ambient temperatures. In addition, it also would be desirable to produce a silicone-substrate composite having a silicone-layer which would fail cohesively instead of adhesively when tested. As used hereinafter, the expression "adhesive failure" means that the silicone layer cleanly separates from the substrate, while in a "cohesive failure" rupture can occur in the silicone layer or in the substrate.